A calibration method, system, equipment and medium for a telescopic workpiece positioning actuator

Abstract

A calibration method, system, equipment, and medium for a telescopic workpiece positioning actuator are disclosed, relating to the field of positioning calibration technology. In the field world coordinate system, a calibration plane is constructed, located within the area that the vertex of the contact can reach. A robotic arm drives the contact in a direction perpendicular to the calibration plane, causing the vertex of the contact to contact multiple measurement points on the calibration plane. The motion data of the contact and the robotic arm in the flange coordinate system are recorded at each contact. Constraint equations are constructed based on the condition that the inner product of any straight line on the calibration plane and the unit normal vector of the plane is zero, combined with the motion data of the contact and the robotic arm in the flange coordinate system, and the optimal solution is obtained. This method addresses the problem that traditional calibration methods are not applicable to telescopic workpiece positioning actuators.

Description

Technical Field

[0001] This invention relates to the field of positioning calibration technology, and specifically to a calibration method, system, equipment and medium for a telescopic workpiece positioning actuator. Background Technology

[0002] A workpiece positioning actuator is a specialized tool installed on a flange at the end of a robotic arm, used to position a workpiece in space by contact. It mainly determines the precise position and orientation of the workpiece in the system coordinate system by physically contacting specific feature points of the workpiece, providing a positioning reference for subsequent assembly or architecture.

[0003] Workpiece positioning actuators typically employ rigid probes, such as pointed cones or ruby ​​ball heads, which make direct, rigid contact with the workpiece during positioning. However, this rigid contact can easily damage workpieces with fragile surfaces. To avoid this damage, we use telescopic probes on the workpiece positioning actuators. When the probe contacts the workpiece, the probe body automatically retracts, reducing the pressure applied to the workpiece surface. The telescopic probe requires calibration of the positioning point during operation to ensure the accuracy of the workpiece positioning actuator's measurement. Furthermore, after prolonged positioning operations, the telescopic probe's extension capacity may degrade, affecting the calibration position of its contact point. Therefore, calibration of the actuator's positioning point is also necessary.

[0004] Traditional actuator positioning point calibration methods generally use the four-point method to determine the positioning point, but this calibration method is time-consuming and not very accurate. In addition, for actuators with telescopic probes, traditional positioning point calibration methods lack the ability to determine the telescopic distance, thus making traditional positioning point calibration methods unsuitable for telescopic workpiece positioning actuators.

[0005] Chinese patent CN115122316A discloses a calibration method and system for the tool center point of a robot. However, this calibration method is also used for rigid measuring rods and cannot be applied to telescopic workpiece positioning actuators.

[0006] Therefore, we propose a calibration method applicable to telescopic workpiece positioning actuators. Summary of the Invention

[0007] The purpose of this invention is to provide a calibration method, system, device and medium for telescopic workpiece positioning actuators, which solves the problem that traditional calibration methods are not applicable to telescopic workpiece positioning actuators.

[0008] This invention is achieved through the following technical solution:

[0009] A calibration method for a telescopic workpiece positioning actuator, specifically including:

[0010] In the on-site world coordinate system, construct a calibration plane, which is located in the area that the vertex of the contact can touch;

[0011] The robotic arm drives the contact head in a direction perpendicular to the calibration plane, so that the vertex of the contact head contacts multiple measurement points in the calibration plane respectively;

[0012] Record the motion data of the contact and robotic arm in the flange coordinate system at each contact;

[0013] Given that the inner product of any straight line on the calibration plane and the unit normal vector of the plane is zero, constraint equations are constructed by combining the motion data of the contact and the robotic arm in the flange coordinate system, and the optimal solution is obtained.

[0014] Furthermore, the calibration plane is referenced by a point on that plane. and the unit normal vector of the plane The construction is carried out, and the calibration plane is touched during the calibration process. Each point is expressed as: ;in For the first in the calibration plane There are 10 measurement points.

[0015] Furthermore, the measurement points are distributed in a grid pattern on the calibration plane.

[0016] Furthermore, the motion data of the contact is the distance from the vertex of the contact to the origin.

[0017] Furthermore, the motion data of the robotic arm includes the rotation matrix of the robotic arm from the flange coordinate system to the world coordinate system, and the position of the origin of the flange coordinate system in the world coordinate system.

[0018] Furthermore, the constraint equation is as follows:

[0019]

[0020] Replacing the measurement point with the vertex of the contact point results in:

[0021]

[0022] in, In order to be with the first When a measurement point touches, the rotation matrix of the robotic arm from the flange coordinate system to the world coordinate system. Let be the origin of the contact in the flange coordinate system. In order to be with the first When the measuring points touch, the distance from the vertex of the contact point to the origin is... This represents the unit vector data for the direction of contact movement in the flange coordinate system. In order to be with the first The position of the origin of the flange coordinate system in the world coordinate system when the measurement points touch.

[0023] Furthermore, the optimal solution to the constraint equations is obtained using the least squares method, the specific process of which is as follows:

[0024] Rewrite the constraint equations as a system of six linear equations in six variables:

[0025]

[0026] when When the system of equations has a least-squares solution;

[0027] Transform the system of six linear equations into a non-homogeneous system of equations:

[0028]

[0029] when When the system of equations has no solution;

[0030] when When the equation system has a unique solution;

[0031] when When the system of equations has a least-squares solution, the least-squares solution is:

[0032] ;

[0033] The solution can be obtained .

[0034] A telescopic workpiece positioning actuator calibration system, comprising:

[0035] The plane construction module is used to construct the calibration plane, and all measurement points on the calibration plane are located in the field world coordinate system;

[0036] The motion control module is used to control the robotic arm to make the contact point touch the measurement point according to the measurement point on the calibration plane;

[0037] The data recording module is used to record the motion data of the contact and the robotic arm in the flange coordinate system after each contact.

[0038] The constraint equation construction module constructs constraint equations based on the condition that the inner product of any straight line on the calibration plane and the unit normal vector of the plane is zero, combined with the motion data of the contact and the robotic arm in the flange coordinate system.

[0039] The calibration module is used to solve the constraint equations.

[0040] An electronic device, comprising:

[0041] Processor, memory, communication interface;

[0042] The memory is used to store the executable instructions of the processor;

[0043] The processor is configured to execute the above-described telescopic workpiece positioning actuator calibration method by executing the executable instructions.

[0044] A readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-described calibration method for a telescopic workpiece positioning actuator.

[0045] The technical solution of the present invention has at least the following advantages and beneficial effects:

[0046] This invention discloses a calibration method, system, equipment, and medium for a telescopic workpiece positioning actuator. By constructing a calibration plane, coordinate system transformation errors of the robotic arm during TCP calibration can be avoided, and the planar geometric conditions lay the foundation for the normal vector inner product constraint. Then, by combining the motion data of the contact and the robotic arm in the flange coordinate system, the calibration of the telescopic workpiece positioning actuator can be satisfied. During contact, vertical touch control can ensure that the contact is subjected to a single force direction, reducing the interference of lateral friction, thereby accurately calculating the unit vector data of the contact origin and the direction of contact movement, improving the accuracy of calibration.

[0047] By using multiple measurement points, a sufficient number of reference points can be ensured during the contact calibration process, thereby further improving the accuracy of the contact calibration. In addition, constructing the calibration plane using reference points and their unit normal vectors ensures that the subsequent constraint equations are constructed more reasonably. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of a method flow of the present invention;

[0049] Figure 2 This is a schematic diagram of a system structure according to the present invention;

[0050] Figure 3 This is a schematic diagram of an electronic device structure according to the present invention. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0052] Example 1

[0053] like Figure 1 The calibration method for a telescopic workpiece positioning actuator shown specifically includes:

[0054] In the on-site world coordinate system, a calibration plane is constructed, which is located in the area that the vertex of the contact can touch. The contact has a hemispherical structure, the center point of which is the origin of the contact, and the vertex of which is the vertex of the contact. The calibration plane is a physical plane. When the contact touches the measurement point of the calibration plane, there will be physical contact feedback, that is, the telescopic probe of the actuator will extend or retract.

[0055] It should be noted that the flatness error of the calibration plane needs to be ±0.02mm; specifically, the calibration plane is based on a reference point on the plane. and the unit normal vector of the plane The construction is carried out, and the calibration plane is touched during the calibration process. Each point is expressed as: ;in For the first in the calibration plane There are 1 measurement point; the reference point is the "anchor point" on the calibration plane, used to locate the plane's position in space, and the unit normal vector of the reference point is the "direction fingerprint" of the plane, uniquely determining its orientation.

[0056] A robotic arm drives the contact head in a direction perpendicular to the calibration plane, causing the apex of the contact head to contact multiple measurement points on the calibration plane; the number of measurement points is... ,Right now middle, ,and The measurement points should be spread out as far as possible and as far away from the reference point as possible;

[0057] In addition, the measurement points are distributed in a grid pattern in the calibration plane; the calibration plane is divided into multiple equally spaced rectangular grids, and the selection of multiple measurement points satisfies the Nyquist sampling theorem, that is, when sampling in the x or y direction of the plane at a spacing Δ, the spatial features of wavelength > 2Δ can be reconstructed without distortion, and since the grid points are uniformly covered in the x or y direction, the accumulation of errors in one direction can be eliminated.

[0058] In addition, the formula for calculating the sampling interval is:

[0059] ;

[0060] ;

[0061] In the formula, For planar dimensions, This represents the number of grid points.

[0062] And the upper limit of spatial frequency satisfies: This is to ensure that minute deformations of the plane are captured.

[0063] Record the motion data of the contact and robotic arm in the flange coordinate system at each contact;

[0064] It should be noted that the motion data of the contact includes the distance from the vertex of the contact to the origin. The motion data of the robotic arm includes the rotation matrix of the robotic arm from the flange coordinate system to the world coordinate system. The position of the origin of the flange coordinate system in the world coordinate system. And rotation matrix It can be calculated based on the kinematic model of the robotic arm, the encoder output, and the relationship between the robotic arm's base coordinate system and the world coordinate system.

[0065] Using the condition that the dot product of any straight line on the calibration plane and the unit normal vector of that plane is zero, constraint equations are constructed based on the motion data of the contact and the robotic arm in the flange coordinate system, and the optimal solution is obtained. This has clear physical meaning. Utilizing the geometric property that "the dot product of the normal vectors at any point in the plane is zero," the contact pose problem is transformed into a linear constraint. Simultaneously, the rotation matrix of the robotic arm from the flange coordinate system to the world coordinate system is used... The position of the origin of the flange coordinate system in the world coordinate system. This connects the flange coordinate system and the world coordinate system, eliminating accumulated transformation errors.

[0066] It should be noted that since the calibration plane is a physical plane, when using this method to calibrate the workpiece positioning actuator, the probe will extend and retract synchronously. Based on multiple recorded data and the solution results obtained from the constraint equations, the origin of the workpiece positioning actuator contact and the unit vector data of the contact movement direction that meet the conditions are finally calculated, thus completing the calibration of the actuator contact.

[0067] Example 2

[0068] As one embodiment, the constraint equation is:

[0069]

[0070] in, In order to be with the first When a measurement point touches, the rotation matrix of the robotic arm from the flange coordinate system to the world coordinate system. Let be the origin of the contact in the flange coordinate system. In order to be with the first When the measuring points touch, the distance from the vertex of the contact point to the origin is... This represents the unit vector data for the direction of contact movement in the flange coordinate system. In order to be with the first When a measurement point touches another point, the position of the origin of the flange coordinate system in the world coordinate system;

[0071] in, , , , and All are known quantities, and the constraint equations contain... For the first in the plane A straight line formed by measurement points and reference points. This part describes the actual pose of the contact, that is, replacing the contact tip with the first contact point. For each measurement point, the physical meaning of the constraint equation is that when the contact point is perpendicular to the contact plane, its actual position must strictly fall on the calibration plane.

[0072] Furthermore, the optimal solution to the constraint equations is obtained by the least squares method, the specific process of which is as follows:

[0073] Rewrite the constraint equations as a system of six linear equations in six variables:

[0074]

[0075] This set of six linear overdetermined equations suppresses local errors at measurement points and improves noise immunity through residual optimization.

[0076] when When the system of equations has a least-squares solution;

[0077] Transform the system of six linear equations into a non-homogeneous system of equations:

[0078]

[0079] when When the system of equations has no solution;

[0080] when When the equation system has a unique solution;

[0081] when When the system of equations has a least-squares solution, the least-squares solution is:

[0082] ;

[0083] The solution can be obtained .

[0084] The physical meaning of this least squares solution lies in the fact that when the contact point contacts multiple measurement points on the calibration plane, measurement noise exists, such as robotic arm positioning errors and flatness errors. Therefore, obtaining the least squares solution... Then, the least squares solution is the standard position of the contact.

[0085] Example 3

[0086] like Figure 2 The telescopic workpiece positioning actuator calibration system shown includes:

[0087] The plane construction module is used to construct the calibration plane, and all measurement points on the calibration plane are located in the field world coordinate system;

[0088] The motion control module is used to control the robotic arm to make the contact point touch the measurement point according to the measurement point on the calibration plane;

[0089] The data recording module is used to record the motion data of the contact and the robotic arm in the flange coordinate system after each contact.

[0090] The constraint equation construction module constructs constraint equations based on the condition that the inner product of any straight line on the calibration plane and the unit normal vector of the plane is zero, combined with the motion data of the contact and the robotic arm in the flange coordinate system.

[0091] The calibration module is used to solve the constraint equations.

[0092] Example 4

[0093] like Figure 3 An electronic device shown includes:

[0094] Processor, memory, communication interface;

[0095] The memory is used to store the executable instructions of the processor;

[0096] The processor is configured to execute the above-described telescopic workpiece positioning actuator calibration method by executing the executable instructions.

[0097] A readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-described calibration method for a telescopic workpiece positioning actuator.

[0098] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A calibration method for a telescopic workpiece positioning actuator, characterized in that, Specifically, it includes: In the on-site world coordinate system, construct a calibration plane, which is located in the area that the vertex of the contact can touch; The calibration plane is referenced by a point on that plane. and the unit normal vector of the plane The construction is carried out, and the calibration plane is touched during the calibration process. Each point is expressed as: ;in For the first in the calibration plane One measurement point; The robotic arm drives the contact head in a direction perpendicular to the calibration plane, so that the vertex of the contact head contacts multiple measurement points in the calibration plane respectively; Record the motion data of the contact and robotic arm in the flange coordinate system at each contact; Given that the inner product of any straight line on the calibration plane and the unit normal vector of the plane is zero, constraint equations are constructed by combining the motion data of the contact and the robotic arm in the flange coordinate system, and the optimal solution is obtained. The constraint equation is: Replacing the measurement point with the vertex of the contact point results in: in, In order to be with the first When a measurement point touches, the rotation matrix of the robotic arm from the flange coordinate system to the world coordinate system. Let be the origin of the contact in the flange coordinate system. In order to be with the first When the measuring points touch, the distance from the vertex of the contact point to the origin is... This represents the unit vector data for the direction of contact movement in the flange coordinate system. In order to be with the first When a measurement point touches another point, the position of the origin of the flange coordinate system in the world coordinate system; The optimal solution to the constraint equations is obtained by the least squares method, and the specific process is as follows: Rewrite the constraint equations as a system of six linear equations in six variables: when When the system of equations has a least-squares solution; Transform the system of six linear equations into a non-homogeneous system of equations: when When the system of equations has no solution; when When the equation system has a unique solution; when When the system of equations has a least-squares solution, the least-squares solution is: ； The solution can be obtained .

2. The calibration method for the telescopic workpiece positioning actuator according to claim 1, characterized in that: The measurement points are distributed in a grid pattern on the calibration plane.

3. The calibration method for the telescopic workpiece positioning actuator according to claim 1, characterized in that: The motion data of the contact is the distance from the vertex of the contact to the origin.

4. The calibration method for the telescopic workpiece positioning actuator according to claim 3, characterized in that: The motion data of the robotic arm includes the rotation matrix of the robotic arm from the flange coordinate system to the world coordinate system, and the position of the origin of the flange coordinate system in the world coordinate system.

5. A calibration system for a telescopic workpiece positioning actuator, based on the calibration method for a telescopic workpiece positioning actuator as described in any one of claims 1-4, characterized in that, include: The plane construction module is used to construct the calibration plane, and all measurement points on the calibration plane are located in the field world coordinate system; The motion control module is used to control the robotic arm to make the contact point touch the measurement point according to the measurement point on the calibration plane; The data recording module is used to record the motion data of the contact and the robotic arm in the flange coordinate system after each contact. The constraint equation construction module constructs constraint equations based on the condition that the inner product of any straight line on the calibration plane and the unit normal vector of the plane is zero, combined with the motion data of the contact and the robotic arm in the flange coordinate system. The calibration module is used to solve the constraint equations.

6. An electronic device, characterized in that, include: Processor, memory, communication interface; The memory is used to store the executable instructions of the processor; The processor is configured to perform the telescopic workpiece positioning actuator calibration method as described in any one of claims 1-4 by executing the executable instructions.

7. A readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the calibration method for the telescopic workpiece positioning actuator as described in any one of claims 1-4.

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